Syria says all of its military and intelligence officials left Lebanon last April. The withdrawal followed intense international pressure after the assassination of former Lebanese Prime Minister Rafik Hariri. Syria had stationed troops in Lebanon since that country's civil war in the 1970s.

Mr. McClellan called on the United Nations to send verification teams back to Lebanon.

U.N. Secretary-General Kofi Annan says he is considering sending such a group to check reports that Syrian intelligence officials may still be operating in the country. A previous U.N. verification team confirmed that all Syrian soldiers had been removed, but said it could not be sure all intelligence agents had left the country.

Mr. McClellan says it is important for the international community to send a clear message to Syria that it must stop meddling in Lebanon. The White House spokesman says Syria's long presence in the country has established a lingering environment of intimidation.